HEAD vs Hackage status report

[Richard Eisenberg]

For future reference (my own future reference, most likely), here are why these packages break:

On Sep 30, 2013, at 2:26 AM, Bryan O'Sullivan wrote:

> 12 language-c-0.4.2        the last parameter of ?Error? is at role Nominal
Legit error. The Error class has Typeable as a superclass, and using GND in that scenario is very dodgy, at best.

> 11 logfloat-0.12.1         the last parameter of ?IArray? is at role Nominal
This should be fixed with "lazier" checking during GND, as detailed here: http://www.haskell.org/pipermail/glasgow-haskell-users/2013-October/022836.html

>  5 diagrams-lib-0.7.1.1    the last parameter of ?Transformable? is at role Nominal
Legit error. The library assumed that a newtype and its base type had the same behavior when passed to a certain type family. It is conceivable that a much-souped-up version of roles could identify that this assumption has been made and then check the assumption, but there are no plans for this.

>  4 smallcheck-1.0.4        the last parameter of ?MonadLogic? is at role Nominal
Error caused by lack of role abstraction.

>  2 monadiccp-0.7.6         the last parameter of ?ReaderM? is at role Nominal
Error caused by lack of role abstraction.

>  2 histogram-fill-0.8.1.0  the last parameter of ?BinEq? is at role Nominal
Legit error. BinEq has a superclass Bin that has an associated type.

>  1 acme-schoenfinkel-0.1.1 the last parameter of ?ArrowApply? is at role Nominal
Error caused by lack of role abstraction.

The "role abstraction" errors could be solved by a rather simple extension to the roles mechanism, I think? I will detail in a fresh email so that the idea doesn't get lost in this thread.

Richard
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